Epigenetics

Why It Matters

Lemarck Revisited

Some of you may have heard of the evolutionary theories of Jean-Batiste Lemarck (1 August 1744 – 18 December 1829). The aspect of this theory he is widely known for is "the inheritance of acquired characteristics". The example of the giraffe's (Giraffa camelopardalis) neck is often cited as an example of how this theory is wrong. However, while natural selection provides a far better explanation for the giraffe's body plan, Charles Darwin (12 February 1809 – 19 April 1882) never fully abandoned Lemarck's theories, and became increasingly Lemarkian in his later years as he struggled with the question of the source of the variation that natural selection acted upon. Darwin struggled partially through his lack of knowledge of genetics. When genetics were finally recognized as a mechanism that explained natural selection and inheritance, natural selection gained much wider acceptance in the scientific community. Unfortunately for Lemarck, this mechanism ran counter to his theories. If DNA was hard coded with information, how could acquired characteristics be passed on? Well, times change and science marches on. Scientists studying the methylation of DNA have identified a mechanism by which acquired traits can be passed to the next generation. There do appear to be limitations as far as the type of acquired information which is passed on but as far as Lemarck? Well, it seems he wasn't all wrong.

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Covers new work with DNA looking at control of DNA expression and the inheritance of acquired characteristics. It also addresses the bigger issue of how scientific theories change as new knowledge is acquired.